2-liter Bottle Rocket Launch to Demonstrate Newton's Laws

Last week in our classes we handed out the first at-home project.  The objective was to build a rocket out of a 2-liter bottle in order to demonstrate Newton's Laws.  I gave the students a lot of leeway on what their rocket could look like, but at a minimum it had to have fins and a nosecone.  There are a couple of items the teacher will need on launch day.  You may already have a bike pump with a gauge at your house, but you will also need to make or buy the rocket launcher. This is the one I have.  It has worked fine for the last couple of years. Although, this one looks a little nicer.

I received a bunch of great rockets and we spent Friday launching them in the parking lot.  This is a great activity and doesn't have to take up a lot of class time.  All of the construction on this project was completed at home.

I did some reading up on how much you should pump each of the bottles up and decided to go a little conservative and keep it about 70-80 psi.  The bottles need to be filled up 1/3 full of water.  There is some debate to the optimal amount of water and would love to hear if you have different findings.

The rockets that went the highest in our class had the straightest fins and also had quite a bit of mass in the nosecone.  We had one rocket that had a tennis ball on the top of the nose and it went twice as high as all of the others.  Here is an example video of what a 2-liter water bottle rockets looks like in action.

http://youtu.be/8VqWPTS_Ubg